The present invention relates to an apparatus for electronically testing printed circuit boards or the like. Specifically, the present invention is directed to such an apparatus of the type including a plurality of substantially parallel test pins for making electrical contacts between respective contact areas of a printed circuit board or the like to be tested and respective of a plurality of resilient contact elements disposed in accordance with a grid of an array plate or the like against which the apparatus is urged, and a mask plate extending at right angles to the test pins and having therein through-bores through which extend the test pins. First ends or tips of the test pins project through the through-bores in the mask plate to engage the contact areas of the printed circuit board.
West German Laid-Open Application (DE-OS) No. 29 33 862 discloses apparatus or an adaptor for electronically testing printed circuit boards and including resilient testing pins to make electric contact between a contact array on a basic grid and a printed circuit board urged onto such apparatus. Each test pin has one tip thereof opposite the contact array to engage a guide channel of the apparatus having the contact array mounted therein and engages in the guide channel a rigid contact element connected through leads to electronic testing means. At its end opposite the printed circuit board under test each test pin has a longitudinally resilient contact tip to engage a through-connected pad on the printed circuit board urged toward the apparatus so as to make electrical contact with such pad.
One shortcoming of test pins of this nature is that the axially resilient contact tips thereof render them relatively complicated and expensive. Also, the diameter of such test pin is relatively great in the area of the resilient contact tip. This may be a major inconvenience due to the ever increasing complexity and packing density of printed circuit boards, which may exhibit local connection pad densities in excess of the average contact density on the basic grid of the contact array. Due to the relatively great diameter of the test pins in the area of the resilient contact tips, adaptation to increasing pad densities no longer will be possible.
There also has been known structure or an adaptor in which the individual test pins do not have resilient contact tips and in which the individual contact elements of the grid-aligned contact array instead are resilient in nature. One shortcoming of this approach is that the springless test pins have to be contoured so as to enable them to be retained longitudinally in the apparatus. Such contour may be obtained, for example, by increasing the diameter of the test pin tips in predetermined portions thereof. This measure limits the possibility of adapting the overall structure to higher pad densities towards the edges of the printed circuit boards. On the other hand, such contour may be obtained also by reducing the test pin tip diameter in certain portions thereof. In that case, however, the stability of the test pin tips will suffer.